TOOLS · UUID
Generate UUIDs, one or fifty at a time.
Random, version 4 UUIDs generated using your browser's own crypto API — free, instant, and never sent anywhere.
What is a UUID?
A UUID (Universally Unique Identifier) is a 128-bit value usually written as 32 hexadecimal characters split into five groups, like 3f2504e0-4f89-11d3-9a0c-0305e82c3301. The point of a UUID is that you can generate one on any machine, with no central authority or database check, and the odds of ever generating the same one twice are so low they're not worth worrying about.
This tool generates version 4 UUIDs, the most common kind — every character in the value (aside from a few fixed version/variant bits) comes from a cryptographically random source. That randomness, not a counter or a timestamp, is what makes v4 IDs practical to generate independently across many systems at once.
How This Tool Works
Generation happens with your browser's built-in crypto.getRandomValues() API — the same cryptographically secure random number source browsers use for things like session tokens. Nothing is sent to a server, and nothing is logged; refresh the page and the UUIDs are gone.
Common Uses
- Primary keys for database rows, especially across distributed systems where auto-incrementing IDs from a single database would create a bottleneck.
- Session tokens, request IDs, or trace IDs for tying logs together across services.
- Unique filenames for uploads, so two users' files never collide.
- Placeholder or seed data for testing.
Frequently Asked Questions
Can two UUIDs ever collide?
Technically yes, but the odds are astronomically small — generating a billion UUID v4 values per second for about 85 years gives roughly a 50% chance of a single collision. In practice it's treated as not happening.
What's the difference between UUID v1 and v4?
v1 UUIDs are built from the current timestamp and the generating machine's network address, which means they can leak when and where they were created. v4 UUIDs are just random bits, with no identifying information embedded — that's why v4 is the default choice for most applications, including this tool.
Are UUIDs safe to use in public URLs?
Yes, in the sense that they can't be guessed or enumerated the way sequential IDs (1, 2, 3...) can. They're not a substitute for real authorization checks, though — anyone with the UUID can still request that resource unless you also check permissions server-side.